[What exactly do genes do, then? What function do they serve? You could start with a consideration of the ~130 genes known to play a role in color. (Any why mutations in those genes alter color.)]

well I'm not going to play like I know all the functions of genes, but what I do know is they are not the end-all be-all of biology. The organism is not defined or controlled by its DNA...instead, the DNA is defined and controlled by the organism. Genes are followers in evolutionary change, not leaders. Genomes resist genetic change and generally only do so as a last resort.

Actually an organism and all of its properties is/are determined by how its DNA interacts with its environment, so I agree that DNA is not the be all and end all of biology. But you cannot willfully change your genetic code (well, maybe if you exposed yourself to some nasty radioactive compounds). DNA does not resort to mutation, it just happens depending on the type of environment you find yourself in. The body does have repair mechanisms in place to prevent mutation as much as possible but it is error prone and not 100% efficient. And so mutations do creep into the genome which results in the change of the organism, thus evolution!

So with other words, a transsexual person just has to wish very hard to become a person of the other gender, to make the Y-Chromosome of all of his cells be instantly transformed into another x-Chromosome and he himself mutating into a woman without the need for a gender reassignment chirurgy (or the other way round for a female to male transsexual)?

Clearly, not a person who ever paid attention in science class. Probably snuck a Bible into his textbook (or, because the Bible's a bit large, maybe a couple Chick Tracts), somewhat like a kid who puts a comic book into his English primer so he doesn't have to read boring shit, except in this case Supersport prefers his shit.

Could've fooled me. You don't have the first clue. You may as well quit now because "The organism is not defined or controlled by its DNA" is exactly opposite the truth. Even much of your behavior is produced by your genes, and you have genes that help with learned behavior too. I think your head would explode if you took a little molecular biology.